Abstract

Detailed field mapping at the east end of the Pine Mountain terrane in central Georgia indicates that the Box Ankle fault is an ∼4-km-thick ductile shear zone separating Grenvillian basement of Laurentian affinity in the footwall from allochthonous accreted terranes in the hanging wall. Fabric data from the Box Ankle fault indicate that it is a gently southeast dipping, northwest-vergent thrust fault. Recently discovered structural relations, together with geochronological data, indicate that the Box Ankle fault is of late Paleozoic age. We argue that the Box Ankle fault is a surface exposure of the Appalachian decollement. The east end of the Pine Mountain terrane may be the only place in the entire orogen where this fundamentally important structure is exposed for study.

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